This invention relates to an ignition timing control for an engine and more particularly to a simplified yet highly effective arrangement for controlling the spark timing of an internal combustion engine.
As is well known, the optimum spark timing curve for an engine is dependent upon a number of factors, primarily engine speed and engine load. A wide variety of mechanical type of devices have been proposed for use with engines and wherein the spark advance can be controlled in response to more than one engine variable. These mechanical systems tend to become rather complicated and cumbersome and are not always as responsive to change in conditions as is desired.
On the other hand, there have been proposed ignition timing controls that are primarily electronic in nature and wherein sensors sense certain engine conditions and output signals indicative of those conditions to an ECU. The ECU is programmed with internal maps and selects the appropriate spark timing from the input parameters and controls the ignition so as to provide the desired timing. Although these systems are quite effective, they tend to be rather complicated. In addition, having a variety of parameters requires a rather large memory capacity.
It is, therefore, a principal object of this invention to provide an improved and simplified ignition timing control for an engine.
It is a further object of this invention to provide a simplified ignition timing control for an engine wherein the timing can be adjusted to be appropriate for all engine conditions without requiring large computer capacities.
In addition to the aforenoted problems in connection with providing optimum spark timing, it has also been recognized that in certain types of engine applications, particularly for use with outboard monors, the actual running conditions and optimum spark timing may vary from cylinder to cylinder depending upon the orientation of the cylinders. This is primarily a function of the fact that in two-cycle engines, the type normally used in outboard motor practice, the interrelationship between the length of the distance between the engine exhaust ports and the discharge point of the exhaust pipe varies from cylinder to cylinder because of the very nature of an outboard motor. These variations require different spark timings for at least some of the cylinders. Obviously, with a purely mechanical system this cannot be accomplished. Furthermore, with electronic systems and in view of the fact that these variations are not linear with either engine speed or engine load, the capability of the memory of the computer is further taxed.
It is, therefore, a still further object of this invention to provide an improved and simplified spark advance system for a multi-cylinder engine wherein the spark timing for different cylinders can be controlled differently.